1. Field
One or more embodiments described herein relate to a display device.
2. Description of the Related Art
A liquid crystal display is one of the many types of flat panel displays currently in use. This type of display includes a liquid crystal layer between a pixel electrode and a common electrode, and data and gate drivers are controlled to generate an image from a plurality of pixels. In operation, the pixel electrode receives a data voltage through a switching element and a counter electrode receives a common voltage. These voltages cause an electric field to be generated in the liquid crystal layer to control transmittance of light, thereby displaying an image.
The liquid crystal display may also receive an image signal from an external graphics controller. The image signal contains luminance information on each pixel, and the data voltage to be applied to each pixel corresponds to the desired luminance information. The data voltage appears as a pixel voltage depending on a difference from the common voltage applied to the common electrode. Each pixels displays luminance represented by a gray scale value of the image signal depending on the pixel voltage.
One effect which degrades the quality of images on a liquid crystal display is known as the degradation phenomenon. This phenomenon occurs when the electric field to the liquid crystal layer is applied in one direction for a long period of time. In an attempt to prevent the degradation phenomenon, the polarity of the data voltage may be inverted respect to a reference voltage on a frame, row, column, or pixel basis. Further, in an attempt to prevent unwanted textures (e.g., a vertical line), the polarity of the pixel voltages of adjacent pixels may set to be different.
Another undesirable effect may occur as a result of the liquid crystal layer. For example, the liquid crystal display may have different response characteristics during the period between when the polarity of the pixel voltage changes from a negative to a positive voltage and when the polarity of the pixel voltage changes from a positive to a negative voltage. For example, the rising speed of the pixel voltage may be slower than a falling speed. The difference in these speeds may cause a change in luminance.
The luminance change may cause problems when the liquid crystal display is driven. For example, differences in luminance may be visually recognized when the liquid crystal display is driven at a relatively low frequency. Referring to a temporal contrast sensitivity function (TCSF), in particular, even though the actual change in luminance may be small when the liquid crystal display is driven at a low frequency, the change in luminance is recognized to be considerable. As a result, flicker may be visually recognized which leads to a degradation in display quality.